The detection of alpha and beta radiation in water samples is complicated by the fact that these forms of radiation are attenuated by water. Current procedures require evaporation of the water in a given sample in order to separate the particulate solids found in the water sample from the water prior to measuring radioactivity. Such practices are described in the International Organization for Standardization (ISO) method 9696 and U.S. Environmental Protection Agency (EPA) method 900.0. The evaporation step, as required in these methods, requires a heat source and electrical power. The additional time needed to perform the evaporation step, along with the requirement for a heat source and electrical power, are generally undesirable for field applications where time, weight, volume, and power requirements pose logistical problems. The present invention overcomes these problems by providing a water sampling device for use with a radiation probe which utilizes a filter means to separate the solids from the water, thereby eliminating the evaporation step. In addition, the device and method of the present invention allow larger volumes of water to be sampled in shorter periods of time, thus enabling short test cycles producing high concentrations of radioactive material collected onto the filter media, if such radioactive material is present in the sample. The device of the present invention can be used with a variety of commercially available radiation probes and is compact, light, and portable. As such, it is well suited for field applications.